Laddaga R A, Chu L, Misra T K, Silver S
Proc Natl Acad Sci U S A. 1987 Aug;84(15):5106-10. doi: 10.1073/pnas.84.15.5106.
The mercurial-resistance determinant from Staphylococcus aureus plasmid pI258 is located on a 6.4-kilobase-pair Bgl II fragment. The determinant was cloned into both Bacillus subtilis and Escherichia coli. Mercury resistance was found only in B. subtilis. The 6404-base-pair DNA sequence of the Bgl II fragment was determined. The mer DNA sequence includes seven open reading frames, two of which have been identified by homology with the merA (mercuric reductase) and merB (organomercurial lyase) genes from the mercurial-resistance determinants of Gram-negative bacteria. Whereas 40% of the amino acid residues overall were identical between the pI258 merA polypeptide product and mercuric reductases from Gram-negative bacteria, the percentage identity in the active-site positions and those thought to be involved in NADPH and FAD contacts was above 90%. The 216 amino acid organomercurial lyase sequence was 39% identical with that from a Serratia plasmid, with higher conservation in the middle of the sequences and lower homologies at the amino and carboxyl termini. The remaining five open reading frames in the pI258 mer sequence have no significant homologies with the genes from previously sequenced Gram-negative mer operons.
来自金黄色葡萄球菌质粒pI258的汞抗性决定簇位于一个6.4千碱基对的Bgl II片段上。该决定簇被克隆到枯草芽孢杆菌和大肠杆菌中。仅在枯草芽孢杆菌中发现了汞抗性。测定了Bgl II片段的6404碱基对DNA序列。汞抗性DNA序列包括七个开放阅读框，其中两个已通过与革兰氏阴性菌汞抗性决定簇中的merA（汞还原酶）和merB（有机汞裂解酶）基因的同源性鉴定出来。虽然pI258 merA多肽产物与革兰氏阴性菌的汞还原酶之间总体上40%的氨基酸残基相同，但活性位点位置以及那些被认为参与NADPH和FAD接触的位置的相同百分比高于90%。216个氨基酸的有机汞裂解酶序列与粘质沙雷氏菌质粒的序列有39%的同一性，在序列中间部分保守性更高，在氨基和羧基末端同源性较低。pI258 mer序列中的其余五个开放阅读框与先前测序的革兰氏阴性菌mer操纵子的基因没有明显的同源性。
